LINEAR DRIVE

Abstract

A linear drive comprising an electric motor driving a worm, a worm gear which meshes with the worm and which is connected non-rotatably to a spindle extending along a linear drive longitudinal axis or axis of rotation and which has a rear and a front end. The worm gear has a bearing seat for a rear bearing, with which the worm gear is mounted in a surrounding transmission housing. To simplify the manufacture of such a linear drive the invention proposes that the rear bearing is in the form of a fixed bearing, the spindle comprises a weldable material, a securing disk is arranged on the rear end of the spindle and the securing disk is connected to the spindle in bonded-material relationship.

Claims

1-14. (canceled)

15. A linear drive comprising an electric motor driving a worm, a worm gear which meshes with the worm and which is non-rotatably connected to a spindle which extends along a linear drive longitudinal axis or axis of rotation and which has a rear and a front end, a spindle nut which is connected to a lift tube and runs on the spindle, a guide tube which relatively moveably accommodates the lift tube, wherein the lift tube is displaceable from a retracted position of being retracted into the guide tube into an extension position of being extended from said guide tube, wherein the worm gear has a bearing seat for a rear bearing with which the worm gear is mounted in a surrounding transmission housing, wherein the rear bearing is in the form of a fixed bearing, that the spindle comprises a weldable material, that a securing disk is arranged on the rear end of the spindle and that the securing disk is connected to the spindle in material-bonded relationship.

16. The linear drive according to claim 15, wherein the securing disk has a central opening so that the securing disk in a peripheral edge region bears in surface contact against the rear end of the spindle to form an overlap.

17. The linear drive according to claim 15, wherein the material-bonded connection is effected by welding, in particular resistance butt welding.

18. The linear drive according to claim 15, wherein the material-bonded connection is effected by welding with an additive material.

19. The linear drive according to claim 15, wherein provided between the securing disk and the worm gear is at least one pairing comprising a projection and a complementary opening or recess, that engage into each other in the installed position.

20. The linear drive according to claim 5 wherein provided at an outer peripheral surface of the securing disk is at least one recess, into which in the installed position a projection of complementary configuration of the worm gear engages.

21. The linear drive according to claim 20, wherein at the outer peripheral surface the securing disk has two diametrally opposite recesses, into which projections of complementary configuration of the worm gear engage.

22. The linear drive according to claim 15, wherein a front plain bearing is provided between the worm gear and the guide tube.

23. The linear drive according to claim 15, wherein the worm gear includes or consists of plastic.

24. A linear drive comprising an electric motor driving a worm, a worm gear which meshes with the worm and which is non-rotatably connected to a spindle which extends along a linear drive longitudinal axis or axis of rotation and which has a rear and a front end, a spindle nut which is connected to a lift tube and runs on the spindle, a guide tube which relatively moveably accommodates the lift tube, wherein the lift tube is displaceable from a retracted position of being retracted into the guide tube into an extension position of being extended from said guide tube, wherein the worm gear has a bearing seat for a rear bearing with which the worm gear is mounted in a surrounding transmission housing, wherein the rear bearing is in the form of a fixed bearing, that a securing disk is fitted with a central opening on to a fitment portion of the rear end of the spindle so that a pass-through portion of the rear end of the spindle projects through the central opening and that the pass-through portion is positively lockingly connected to the securing disk by orbital riveting.

25. The linear drive according to claim 24, wherein the pass-through portion projects by about 2-4 mm beyond a rear surface of the securing disk.

26. The linear drive according to claim 24, wherein the central opening in the securing disk is of a profiled or non-round configuration.

27. The linear drive according to claim 24, wherein a clearance fit is provided between the central opening of the securing disk and the outer peripheral surface of the spindle.

28. The linear drive according to claim 24, wherein the securing disk forms a part of the one inner race of the rear bearing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Finally in relation to a plurality of identical components or elements, for reasons of clarity, only a respective one is denoted by a reference numeral.

[0037] In the drawings:

[0038] FIG. 1 shows an isometric view of the linear drive from the front,

[0039] FIG. 2 shows a longitudinal section through the linear drive shown in FIG. 1,

[0040] FIG. 3 shows an isometric enlarged view of the assembly including the spindle nut fitted on to the rear end of the spindle, the fitted rear bearing and the securing disk connected to the spindle,

[0041] FIG. 4 shows an isometric exploded view of the assembly shown in FIG. 3,

[0042] FIG. 5 shows an isometric enlarged view of an alternative embodiment of the assembly including the spindle nut fitted on to the rear end of the spindle, the fitted rear bearing and the securing disk connected to the spindle,

[0043] FIG. 6 shows an isometric exploded view of the assembly shown in FIG. 5, and

[0044] FIG. 7 shows an end view of the securing disk of the embodiment shown in FIGS. 5 and 6.

DETAILED DESCRIPTION

[0045] Accordingly the linear drive shown in its entirety in FIGS. 1 and 2 substantially comprises an electric motor accommodated in a motor housing 2 extending transversely relative to a transmission housing 4.

[0046] Accommodated in a front end of the transmission housing 4 is a guide tube 6 which in turn relatively moveably accommodates a lift tube 8 which is displaceable along a longitudinal axis of the linear drive by means of a spindle nut displaceable on a spindle. Thus the lift tube can be displaced axially along the longitudinal axis of the linear drive from an end position of being retracted into the guide tube 6 into an end position of being extended out of the guide tube by way of the transmission accommodated in the linear drive.

[0047] Carried on the front end of the guide tube 6 is a sealing head portion 14 which prevents the ingress of water between the guide tube 6 and the lift tube 8.

[0048] A rear fork head 10 is fitted into or alternatively formed on the rear end of the transmission housing 4. A front fork head 12 is fixed to the front end of the lift tube 8. By way of that fork head 10, 12 the linear drive is held for example between the underside frame of a bed and the pivotable frame part, for example a head or foot part, that is to be displaced, or it is fixed there with struts which can thus be displaced relative to each other by the lift tube 8 being extended out of the guide tube 6 and retracted into same again.

[0049] FIG. 1 shows the linear drive with the lift tube 8 partially extended.

[0050] Referring to FIG. 2, displacement of the lift tube 8 is effected by way of the electric motor which is accommodated in the motor housing 2 and which drives a shaft with a worm 14 arranged thereon at the end and which in turn meshes in known manner with a worm gear 16. Fitted into that worm gear 16 is a steel spindle 18 on which there runs a spindle nut 20 connected to the lift tube 8.

[0051] At a rear end facing away from the lift tube 6 the worm gear 16 has a rear bearing seat 16a on which the inner race of a bearing 24 is carried, the outer race thereof being accommodated in the surrounding transmission housing 4. The outer race of the bearing 24 sits in a bearing receiving means 4a of the transmission housing 4, that forms an abutment at both sides for the outer race of the bearing 24 so that it is therefore fixedly accommodated in the transmission housing 4 and can carry and transmit both radial and therefore also axial forces. That bearing 24 which is in the form of a fixed bearing can thus represent the single bearing for supporting the spindle 26 with the worm gear 16 in the transmission housing 4.

[0052] The bearing 24 is fixed by way of a securing disk 26 which is welded in material-bonded relationship to the rear end of the spindle and which preferably also comprises steel and the outside diameter of which in the present case is larger that the outside diameter of the steel spindle 18 and the bearing seat 16a.

[0053] The securing disk 26 which is also shown isometrically in the exploded view in FIG. 4 has in the outer peripheral surface in diametrally opposite relationship two recesses 26a, 26b into which two complementary pin-like projections 16b, 16c at the rear end of the bearing seat 16a engage and thus at the same time provide the non-rotary connection between the spindle 26 and the worm gear 16. The securing disk further has a central opening 26c which extends continuously in the longitudinal direction from the front face to the rear face. Thus the overlap region between the spindle end face and the securing disk end face is formed between the outer radius of the spindle and the inner radius of the central opening 26c; it is with the overlap region that the securing disk 26 bears in the installed position at the end against the rear end of the steel spindle and in that region is connected to the spindle in material-bonded relationship. Accordingly the region between the outer peripheral surface of the steel spindle 18 and the inner peripheral surface of the central opening forms the overlap, that is to say the annular surface at which the steel spindle 18 bears at the end against the inner face of the securing disk 26.

[0054] Actuation of the worm 14 by way of the electric motor thus causes rotation of the worm gear 16 and the steel spindle 18 non-rotatably accommodated therein, whereby the spindle nut 20 provided with the complementary female thread is displaced on the spindle 18 within the stationary guide tube 6. It is sometimes possible that that overlap region is at least portion-wise interrupted by the recesses 26a, 26b. That however does not undermine the durability.

[0055] In the embodiment shown in FIG. 5 the securing disk 26 is fitted with its central opening on to an attachment portion of the rear end of the spindle 18. In that case the spindle 18 projects through the central opening and is connected in positively locking relationship to the securing disk 26 by means of orbital riveting. FIG. 5 shows that by the mushroom-like enlargement of the outer diameter of the spindle 18 at its free end directly beside the securing disk 26.

[0056] The exploded view in FIG. 6 illustrates the arrangement ready for assembly as shown in FIG. 5.

[0057] In this case the spindle 18 is solely sawn off and its end is in a substantially burr-free state. The securing disk 26 can be clearly seen, which in this embodiment is provided with three radially outwardly extending, peripherally mutually spaced recesses 26a, 26b distributed uniformly about the central opening 26c. In this case the central opening 26c is adapted to be fitted directly on to the thread flights of the spindle 18.

[0058] In another embodiment which is not shown in detail here the spindle at the rear end has a reduced-diameter step to which the central opening 26c corresponds.

[0059] Furthermore FIG. 6 shows three projections 16a, 16b, 16c which are provided extending in the axial direction on the worm gear 16 in the region of the bearing seat 16a in mutually peripherally spaced relationship, in particular being formed in one piece thereon. After assembly those projections 16a, 16b, 16c engage into the recesses 26a, 26b so as to produce a non-rotatable connection between the worm gear 16 and the securing disk 26. It is not possible here to see the female thread of the worm gear 16, as is shown by the views in FIGS. 2 and 3. For fitment of the worm gear 16 on to the spindle 18 it is screwed on to the spindle. After assembly is effected the female thread of the worm gear 16 and the male thread of the spindle 18 form a play-free connection so that axial forces can be transmitted in the longitudinal direction of the spindle 18 to the worm gear 16 and the bearing seat 16a thereof.

[0060] FIG. 7 shows the securing disk 26 viewing on to the rear face thereof. The three recesses 26a, 26b, 26c are arranged at uniform angular displacements projecting radially outwardly around the central opening. The outer diameter of the spindle 18 is further illustrated by a dash-dotted line and it can be seen that there is a slight clearance between the outside diameter of the spindle and the internal width of the central opening for simplified fitment of the securing disk 26 on the spindle 18. The central opening 26d with a non-round internal cross-section can also be clearly seen. Between the recesses 26a, 26b, 26c the internal contour of the securing disk 26 is admittedly substantially round but those portions involve a smaller radius than the spindle 18. The central opening 26d of the securing disk 26 is thus provided with further profilings and is accordingly of a non-round configuration. During assembly and in particular during the orbital riveting process the outside diameter of the spindle 18 enlarges and fits snugly to the profilings or to the non-round configurations of the central opening 26d in such a way that after assembly there is a positively locking and non-rotatable connection between the spindle 18 by way of the securing disk 26 to the worm gear 16 and at the same time a positively locking connection, which is non-displaceable in the longitudinal direction of the spindle 18, is formed between the securing disk 26 and the spindle 18 so that the inner race of the bearing 24 is fixed at both sides, both by the shoulder of the worm gear 16 on the one hand and also by the securing disk on the other hand, and is to be classified as a fixed bearing relative to the spindle 18.

LIST OF REFERENCES

[0061] 2 motor housing [0062] 4 transmission housing [0063] 4a bearing receiving means [0064] 6 guide tube [0065] 8 lift tube [0066] 10, 12 fork head [0067] 14 sealing head portion [0068] 16 worm gear [0069] 16a bearing seat [0070] 16b, 16c projection [0071] 18 steel spindle [0072] 20 spindle nut [0073] 24 bearing [0074] 26 securing disk [0075] 26a, 26b recess [0076] 26c central opening